Acid-proof cement lining for digesters of sulphite pulp



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106. COMPOSITIONS,

COAllNG OR PLASTIC ment to be used as a linin No Drawing.

Patented May 6, 1924.

M Cross I Reference PATENT OFFICE.

' Examiner NAOKI TAKA'I/A, or roxvo, JAPAN.

ACID-PBOOF CEMENT LINING FOR DIGESTEBS OF SULPHITE PULP.

To all whom it may oonmrn:

Be it known that I, Neon Tamra, a subject of the Emperor of Japan, and a resident of No. 19 Ohara-Cho, Koishikawa-Ku, city of Tokyo, Empire of Japan, have invented new and userul Improvements in Acid- Proof Cement Linings for Digesters of Sulphite Pulp, of WhlOh the following is a specification.

This invention relates to a process of preparation of acid proof, rapid setting ceof digester of sulphite pulp, and has for its object to obtain cement which can be used a long period without cracking, collapsing, stripping or etching under the action of sulphurous or sulphuric acid even in high pressure and temperature.

According to the present invention the process consists in mixing white clay, lime or calcium carbonate, infusorial earth, asbestos and boric acid or borax thoroughly and the mixture is heated and. admixed with lead oxide and the product thus obtained is a plied as lining in the state of mud by knea m' with sodium silicate solution. An exam e for carry e invention is as fo ows. The mixture of parts of clay. 10 parts of lime, 3 parts of infusoria car 1, 3 parts of asbestos and pa s 0 ran is heated, p ggy ere after cooling and admixed witli '1'0 partsb'f lead oxide owder:

er ivel boric acid or its salt and other materia s may eated and dered separately and then may be mixed. In general, as silicate has a strong acid resisting property white clay is used as the chief component in the present invention. Lime forms acid proof, insoluble.calcium silicate by reacting with soluble silicates and also forms calcium sulphite by the action of acid sulphite solution during the digestin operation and a small part of calcium su p ite thus formed passes to calcium sulphite. These calciumsalts are all white, minute, acid proof substances and have the effect of increasing the acid resisting property of mortar. As infusorial earth has a property of increasing the minuteness an water proofing character of mortar, it prevents the penetration of bisulphite solution. Asbestos 1s a acid proof substance and its fibrous state contributes to the firmness of mortar after setting. Boric acid combines with lead, cal- Application filed February 1, 1922; Serial No. 533,400. 7?

in a furnace, powdered cium, etc., and forms a white insoluble, minute substance having a water proof property'. Thus, boric acid or borax in mortar forms insoluble salts'of lead and calcium, etc., and distributes through the whole mass of mortar after setting. According to thefact, such mortar is very compact in quality and does not allow the penetration of liquid and moreover its resisting (power a amst sulphuric and sulphurous aci is very arge.

Again, lead oxide forms lead silicate by seta; ting or remains as the origma orm which;

though gradually passes to lead sulphate or sulphite by the action of sulphuric or sulphurous acid during the digesting o eration, yet these resulting compounds are. w ite, minute substances of acid resisting roperty and have the effect of preventing the penetration of liquid and also accelerate the time of setting.

'Heretofore, the difliculty of, bisulphite pulp manufacture may be said to lie in the iniug of digester and the difliculty of lining exists solely in cement. Desi s heretofore published with respect to sucfi cement have not suflicient efi'ect in practice. Again, as such kind of cement imported from Sweden to Japan requires about 30 seconds for the setting of the degree of supporting the inner lining in arch part, it results in uneven setchange of temperature and pressure by discharging operation. Moreover, as such cement materials are not heated, it collapses and strips gradual] by the action of acid liquor, evolvin car nic acid .gas and hydrogen sulphi e. Again, the coarseness of the quality of siliceous substance in the said cement results in unhard and uncompact lining after setting and permits the penetration of acidic humor with the result of etching and cclla sing when treated under high pressure. is present invention has obviated these dificulties and the character- 'istics lies in admixing boric acid or borates to the common components of lining cement,

followedby heatin and powdering. Boric acid or borates, w on heated with lime in presence of silica or silicates, forms calcium salts by combininlg with lime at hlgh temperature and fina y passes to very complex substance by combining-with silica or silicates. The said com lex substances is amorphous in nature an has a strong acid resisting property. Moreover, its small covIll) g 1,4e2,aea

. k eflicient of expa'hsi'oxfi is especially beneficial to the use of lining sulphite digester which suffers abrupt change of temperature. Boric acid or borates forms calcium salt by setting and according to experiments it acof calcium silicate and makes the whole mass and tough. During the digesting 0 ration a sma 1 part of borate in the neigh rhood of the surface may be dissolved by sulphurous acid yet the minute articles of calcium sulphit replace it and makes the surface compact and strong, thereby preventing the penetration of liquid. The cement of the present invention is far cheaper than similar acid resisting ones, sets rapidly, forms no cracking and the mass after setting is compact and tough and has a high acid rcsisting property. Moreover, its small coeflicie-nt of expansion allows the use for a long period without fear of cracking or colla sing. Again, the selection of raw materia is easy as heating operation is emand at mixing t ployed in the present invention for the preparation of cement.

aving now particularly described and ascertained the nature of my said invent-ion and in what manner the same is to be p'erformed, I declare that what I claim is The method of making an acid proof, se ingredient for use in lining a sulphite pulp digester, consisting in mixing substantial y 60 parts of white clay, substantially arts of lime, substantially 3 parts of asldestos and substantiall 6 arts of bo eatin such mix- WMM a ter cooling, he same with substantially 10 parts of lead oxide powder.

in presence of two witnesses.

g V NAOKI TAKATA.

Witnesses:

MA'rsoooao OTsUKA, KENJIRO TXKANZKAL In testimony whereof I aflix my signature 

